A stranger was roaming around. Black-haired, big, and handsome, he'd wandered into town a few days earlier and was looking for some action. Right now he was hanging out near some young females – twins, by the looks of them – and hoping to get to know them a little better. But unfortunately for him, it wasn't to be. Just as he was getting comfortable, their mom and dad showed up.

Two gray wolves, a few hundred yards south, their thick winter fur silhouetted against the snow. They took off toward the interloper at a dead sprint, two blurs racing along the frozen creekbed. The new wolf, sizing up the scene, tucked his tail between his legs and ran away – the lupine equivalent of a teenage boy fleeing his girlfriend's house with his jeans in his hand, her dad standing on the front porch with a shotgun. He raced across a road, an unnatural barrier the wolves normally don't like to cross, and his pursuers gave up the chase. With one eye still on the intruder, they sauntered back to the pack and led a triumphant group howl.

It was shortly after dawn in the Lamar Valley, a snow-covered basin near the northern edge of Yellowstone National Park, not far from the Montana-Wyoming border. I was there with a dozen other wolf enthusiasts for Lamar Valley Wolf Week, a periodic field seminar organized by the Yellowstone Association, the park's nonprofit educational arm. Owing to its preponderance of wildlife and relative accessibility, Lamar Valley is probably the best place in the world to see wolves in the wild – especially during winter, when their prey move to lower elevations and the wolves are easier to spot in the snow. For three days, my classmates and I were going to pursue them in their natural habitat – watching, listening, and, most of all, waiting.

Wolves have become a controversial topic lately. As the federal government has lifted some endangered-species protections for the gray wolf, more states have made hunting them legal, sparking heated clashes between sportsmen and wildlife advocates, ranchers and conservationists. Wolves – thanks to their primal ferocity, centuries of mythology and folklore, and a social structure strikingly similar to our own – inspire emotions in a way that, say, the reticulated toadfish does not. But I wanted to move past the politics and see these storied animals up close – or at least as close as one can get to an elusive predator with an innate fear of humans and a nose that can detect us from miles away.

Our guide for the week was 30-year-old wolf expert John Harmer. A Houston native who majored in poultry science at Texas A&M before deciding chicken farming was not his calling, he'd come to Yellowstone for a three-week training course two years earlier. By the time it ended, he'd finagled himself a job. Now, he lives a mile from the park and leads various wildlife courses throughout the year. On his days off, he goes hiking and looks for wolves.

Until humans decided to tame it, Yellowstone had been home to wolves for millennia. They were wiped out in the 1920s as part of a systematic eradication by park rangers, during which hundreds of wolves were trapped, poisoned, and shot. However, since their reintroduction to the park 18 years ago, they've been one of the conservation movement's biggest success stories. The population now hovers somewhere around 80, spread among nine constantly evolving packs. A group called the Yellowstone Wolf Project keeps tabs on all of them, outfitting a few wolves in each pack with radio or GPS collars to make its task easier. (Researchers name the wolves alphanumerically, according to sex and the order in which they were collared – e.g., 690F. Uncollared wolves get nicknames like Big Blaze, Casanova, and Puff.) So far, the researchers have gathered information not only on the wolves' behavior and biology but also on their importance to the rest of the Yellowstone ecosystem – due to a phenomenon known as trophic cascade, in which their presence as predators sets off a chain reaction that impacts species from elk to cottonwood. (Wolves eat the former, which leads to a resurgence of the latter.)

The wolves we were watching – the ones who'd chased off the intruder – were the Lamar Canyon pack, or the Lamars for short. The pack consists of 12 wolves: the alpha male, 755M; the alpha female, 832F; two females, both two years old, that the black stranger was flirting with; four yearling females; and four 10-month-old pups, who were, at the moment, tumbling in the snow. We watched the pups play as the rest of the pack looked on. Then, with the alpha female in the lead, they made their way up a nearby hill, padding single file through the snow before disappearing over the ridgeline.

The Lamars used to include another adult male, 754M, who was 755M's brother. A big, gentle wolf who liked to babysit the pups, he also never shied from a fight – like the time he led the pack into battle against some encroaching wolves from the Agate pack, charging full speed on what was later discovered to be an injured leg. A few weeks before our visit, though, 754M had been shot outside the park during a legal hunt in Wyoming. The state legalized wolf hunting last fall, just a day after wolves were taken off the endangered-species list. It was the fifth state to do so, and following Montana and Idaho, the third that borders Yellowstone. Hunting is still prohibited within the park, but there's nothing keeping hunters from setting up right outside.

The next morning was chilly and wet. The Lamar pack had disappeared into an area called Cache Creek to hunt; Harmer didn't expect to see them again for a few days. Instead, we went looking for some of the park's lesser-known packs: the Blacktails, the Junction Buttes, the 8 Miles. When that proved difficult, we went on a hike up to an old den site, a hole dug out under a big tree where the alpha female known as 9F – the Eve-like matriarch of, at one point, roughly 70 percent of Yellowstone's wolves – raised a pup that would grow up to lead a pack called the Druids. The Druids are defunct now, but for a while, they were the most famous wolf pack in the world. If you've seen a documentary about wolves, it was almost certainly about them.

With the Lamars out of sight, finding wolves was tougher than expected. On the other hand: If you're not going to see wolves, there's no better place to not see them than Yellowstone in winter. The park is majestically empty, devoid of the theme-park masses who crowd it in the warmer seasons. The bears had already gone into hibernation, but we saw loads of other wildlife: bison, elk, pronghorn, coyotes, ravens, and eagles. One day, a friend and I hiked up a trail called Specimen Ridge, where a snow-peaked Mount Washburn towered in the distance and the ice-cold Yellowstone River wound its way through steaming geothermal vents in the canyon below. We saw a set of fresh mountain lion prints in the snow, atop some also-fresh deer tracks – a real-time picture of nature at work.

The next day, there was no sign of wolves at all. We made our way from lookout to lookout, scanning the treelines and gullies for movement. After a few hours, we'd driven all the way out of the park. Wind-bitten and slightly frustrated, we were headed back to our cabins when a call came over the radio from a Wolf Project researcher named Rick McIntyre: "So, all we've got right now are a couple of lumps...." That was good enough for us. We lugged our scopes to the top of a hill, where Rick and his crew were peering into the distance. About a mile away, seven wolves from the Junction Butte pack were huddled on a snowy slope under some pines, about to bed down for the night. They were far away and tiny, no bigger than a Magic Marker dot – but a thrilling sight regardless.

Our final morning in the park, my buddy and I woke early and set out alone. A snowstorm had blown through overnight, and all of Yellowstone was covered in a fresh coat of white. Familiar landscapes looked totally different: It was like seeing a whole new park. We drove to a lookout called Little America and trained our scopes on a herd of elk below, bunched in a group and looking skittish – possible signs of a nearby wolf. Snow had started to fall again, and through the lens, the elk looked like figurines in a snow globe. We blew into our hands and waited.

Unfortunately, we never matched that first morning with the Lamars. Two days later, we found out why. On December 6 – two days after we saw her lead her pack into the mountains – wolf 832F was shot and killed by a hunter 15 miles outside the park. She was the eighth Yellowstone wolf killed by hunters this year, the fifth who was collared. Four days later, the Montana Fish, Wildlife & Parks Commission voted to temporarily halt hunting in areas bordering the park; the chairman stressed that the move was not permanent, and was intended only to address the "particular and unique situation" of collared wolves being killed. In the rest of Montana and Wyoming, meanwhile, the hunting season went on.